Chemokines are small cytokines which act as chemoattractants for leukocytes, coordinating both homeostatic trafficking of these cells as well as recruiting specific cell populations to sites of inflammation. Chemokine dysregulation is considered to play a part in a wide spectrum of human diseases involving the immune system including inflammation and autoimmunity (1).
The human eotaxin family includes three known cytokines which belong to the CC chemokine family:
Eotaxin 1 (eosinophil chemotactic protein 1, also termed eotaxin or Chemokine (C—C motif) ligand 11 (CCL11)) is known to selectively recruit eosinophils by inducing their chemotaxis and therefore, is implicated in allergic responses.
Eotaxin 2 (eosinophil chemotactic protein 2, also termed Chemokine (C—C motif) ligand 24 (CCL24), myeloid progenitor inhibitory factor 2 (MPIF-2)) is a potent chemo attractant for inflammatory cells including eosinophils (2-4), basophils (4), Th2-type lymphocytes (5) and neutrophils. Eotaxin-2 is expressed in various types of endothelial cells (5-9), and induces angiogenic and migratory responses in endothelial (10) and smooth muscle cells (11).
Eotaxin 3 (eosinophil chemotactic protein 3, Chemokine (C—C motif) ligand 26 (CCL26), Macrophage inflammatory protein 4-alpha (MIP-4-alpha), Thymic stroma chemokine-1 (TSC-1), and IMAC) is chemotactic for eosinophils and basophils.
Eotaxin-2 is only 39% homologous to eotaxin, and the two polypeptides differ almost completely in the NH2-terminal region (12). Eotaxin-2 is located on chromosome 7q11.23 and eotaxin is located on chromosome 17q21.1. The eotaxin-3 gene lies close to the eotaxin-2 gene on chromosome 7 but shares only 33% homology with it. These chemokines bind specifically to the CCR3 receptor. CCR3, the eotaxin receptor, is a 7-transmembrane G protein-coupled receptor which is expressed by eosinophils as well as by a wide array of cell types including macrophages and endothelial cells (13).
WO 97/00960 discloses nucleic acids which encode human eotaxin (CCL11), as well as isolated or recombinant human eotaxin proteins. WO 97/00960 also discloses methods of use of the eotaxin proteins in the recruitment of eosinophils to a particular site or in the treatment of allergic conditions.
CCR3 expression was originally studied in the pathogenesis of asthma and allergy, where it continues to serve as a therapeutic target (14). More recently however, a role for this pathway has emerged in the study of additional inflammatory and autoimmune disorders including inflammatory bowel disease (15), multiple sclerosis (16) and rheumatoid arthritis (RA).
Rheumatoid arthritis (RA) is a common, chronic inflammatory disease, characterized by intense, destructive infiltration of synovial tissue by a broad spectrum of inflammatory cells (17). Multiple cytokines, derived from macrophages and fibroblasts are responsible for the secretion of both cytokines and chemokines in (RA) (18). The accumulation of leukocytes in the joint space leads to secretion of tissue degrading factors, including cytokines and matrix degrading enzymes.
Chemokine inhibition has previously been tested as a therapeutic option in adjuvant induced arthritis, a commonly used animal model of RA (19). Using the same model, CCR3 has been shown to play a role in recruitment of leukocytes to synovial tissue (20). Differential expression of many chemokines and chemokine receptors has also been demonstrated in serum and synovial tissue of RA patients (21).
Inflammation with involvement of cytokines and chemokines is thought to play a pivotal role also in promoting atherosclerotic plaque growth and propensity to destabilize and subsequently rupture (22, 23). Eotaxin/CCL24 receptor (CCR3) is expressed in plaque macrophages (24). A clinical study demonstrated that in a cohort of healthy men, a non-conservative polymorphism in the eotaxin gene has been associated with increased risk for myocardial infarction (25). In a subsequent study, it has been found that increased circulating eotaxin level is associated with the presence of coronary atherosclerosis and ischemia (26, 27).
Atherosclerosis is a process in which fat deposition progresses in the arterial wall leading to progressive narrowing of the lumen. The mature plaque is composed of two basic structures: the lipid core and the fibrous cap. The smaller the lipid core and the thicker the fibrous cap, the more stable the plaque is, meaning that its propensity to rupture and cause myocardial infarction or unstable angina are decreased. It is now clear that most plaques that cause acute coronary syndromes (e.g., myocardial infarction and unstable angina) are angiographically shown to have <70% stenosis (reviewed in 28, 29). Approximately 60% of these lesions are caused by rupture of plaques with a large thrombogenic core of lipid and necrotic debris (including foci of macrophages, T cells, old hemorrhage, angiogenesis, and calcium). The ruptured cap is thin, presumably because macrophages secrete matrix metalloproteinases that digest it as they move across plaque, and because smooth muscle cells (the supporting element of the plaque) are depleted due to senescence or apoptosis caused by several factors, such as inflammatory cytokines.
WO 06/93932 discloses methods for the detection or diagnosis of atherosclerosis by measuring the level of eotaxin in an individual's serum. The application further suggests that detection of elevated eotaxin levels in serum may provide a means to diagnose atherosclerosis prior to the onset of symptoms.
None of the above publications teach or suggest eotaxin-2 as a target for therapeutic intervention for the treatment of inflammatory, autoimmune or cardiovascular diseases.